Systems and methods for determining the composition of gaseous fuel

ABSTRACT

Disclosed are methods, systems, and computer-readable mediums for determining the composition of gaseous fuel. An initial gaseous fuel stream is provided that includes methane, non-methane hydrocarbons, and inert gases. Air is mixed into the initial fuel stream upstream of a first catalyst. The first catalyst oxidizes only the non-methane hydrocarbons of the initial fuel stream to produce a resultant fuel stream comprising methane and inert gases. Air is mixed into the resultant fuel stream downstream of the first catalyst and upstream of a second catalyst. The second catalyst oxidizes only the methane hydrocarbons of the resultant fuel stream to produce an output fuel stream. Mole ratios of the methane, the non-methane hydrocarbons, and the inert gases of the initial fuel stream are each determined.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. national stage application claimingthe benefit of International Application No. PCT/ US2015/045516, filedon Aug. 17, 2015, which claims the benefit of priority to U.S.Provisional Patent Application No. 62/039,563, filed Aug. 20, 2014,titled “ SYSTEMS AND METHODS FOR DETERMINING THE COMPOSITION OF GASEOUSFUEL.” Both applications are incorporated herein by reference in theirentirety.

BACKGROUND

A “raw fuel” stream typically refers to fuel that is obtained from awell. Often, such fuels are also referred to as “raw well head gases.”Raw well head gases can be used by spark ignited piston engines in orderto power generators, pumps, compressors, etc., that are employed for avariety of applications. In order to tune and optimize engineperformance, it is desirable to know the relative amounts of methane,non-methane hydrocarbons, and carbon dioxide in the raw well head gassupplying the engine. This is because engine performance is oftenlimited by autoignition of a fuel charge, which causes the phenomenonreferred to as “knock,” An engine experiencing knock can quickly bedestroyed or otherwise damaged. Methane is very resistant to knock.However, most non-methane hydrocarbons are less resistant to knock, andtherefore they tend to reduce engine performance as compared to methane.Carbon dioxide is an inert gas and does not contribute to the energy ofthe fuel. Accordingly, when carbon dioxide is present in a fuel, moretotal fuel must flow to maintain a certain engine power. Thus, knowingthe composition of the fuel enables adjustments to engine configurationsand the relative amounts of fuel required, which can improve engineperformance and avoid potentially damaging engine knock.

SUMMARY

Disclosed herein are methods, systems, and computer-readable mediums fordetermining the composition of gaseous fuel. One embodiment relates to amethod. The method comprises: providing an initial gaseous fuel streamat a fuel mass flow rate, wherein the initial fuel stream comprisesmethane, non-methane hydrocarbons, and inert gases; mixing air into theinitial fuel stream upstream of a first catalyst, wherein the air is ata first air mass flow rate; oxidizing, by the first catalyst, only thenon-methane hydrocarbons of the initial fuel stream to produce aresultant fuel stream comprising methane and inert gases; mixing airinto the resultant fuel stream downstream of the first catalyst andupstream of a second catalyst, wherein the air is at a second air massflow rate; oxidizing, by the second catalyst, only the methanehydrocarbons of the resultant fuel stream to produce an output fuelstream; and determining, using one or more processors, a mole ratio ofthe methane of the initial fuel stream, a mole ratio of the non-methanehydrocarbons of the initial fuel stream, and a mole ratio of the inertgases of the initial fuel stream, wherein the determination is based onthe fuel mass flow rate, the first air mass flow rate, and the secondair mass flow rate.

Another embodiment relates to a device for determining a relativecomposition of gaseous fuel. The device comprises a pump configured todirect an initial gaseous fuel stream over a first catalyst at a fuelmass flow rate, wherein the initial fuel stream comprises methane,non-methane hydrocarbons, and inert gases. The device further comprisesa first mass flow controller configured to provide air at a first airmass flow rate to mix into the initial fuel stream upstream of the firstcatalyst. The device further comprises the first catalyst, configured tooxidize only the non-methane hydrocarbons of the initial fuel stream toproduce a resultant fuel stream comprising methane and inert gases. Thedevice further comprises a second mass flow controller configured toprovide air at a second air mass flow rate to mix into the resultantfuel stream downstream of the first catalyst and upstream of a secondcatalyst. The device further comprises the second catalyst, configuredto oxidize only the methane hydrocarbons of the resultant fuel stream toproduce an output fuel stream. The device further comprises one or moreprocessors configured to determine a mole ratio of the methane of theinitial fuel stream, a mole ratio of the non-methane hydrocarbons of theinitial fuel stream, and a mole ratio of the inert gases of the initialfuel stream, wherein the determination is based on the fuel mass flowrate, the first air mass flow rate, and the second air mass flow rate.

Another embodiment relates to a system. The system comprises a fuelsource configured to supply an initial gaseous fuel stream that isdirected over a first catalyst at a fuel mass flow rate, wherein theinitial fuel stream is a raw well head gas that comprises methane,non-methane hydrocarbons, and inert gases. The system further comprisesa first mass flow controller configured to provide air at a first airmass flow rate to mix into the initial fuel stream upstream of the firstcatalyst. The system further comprises the first catalyst, configured tooxidize only the non-methane hydrocarbons of the initial fuel stream toproduce a resultant fuel stream comprising methane and inert gases. Thesystem further comprises a second mass flow controller configured toprovide air at a second air mass flow rate to mix into the resultantfuel stream downstream of the first catalyst and upstream of a secondcatalyst. The system further comprises the second catalyst, configuredto oxidize only the methane hydrocarbons of the resultant fuel stream toproduce an output fuel stream. The system further comprises a mastercontroller comprising one or more processors. The one or more processorsare configured to: control the first mass flow controller to adjust thefirst air mass flow rate; control the second mass flow controller toadjust the second air mass flow rate; determine a mole ratio of themethane of the initial fuel stream, a mole ratio of the non-methanehydrocarbons of the initial fuel stream, and a mole ratio of the inertgases of the initial fuel stream, wherein the determination is based onthe fuel mass flow rate, the first air mass flow rate, and the secondair mass flow rate; and transmit the determined mole ratios to acontroller of an engine configured to combust the raw well head gas.

Still another embodiment relates to a method. The method includesproviding an initial gaseous fuel stream having a methane hydrocarbon,non-methane hydrocarbon, and an inert gas at a fuel mass flow rate;mixing air at a first air mass flow rate into the initial gaseous fuelstream upstream of a first catalyst; oxidizing, by the first catalyst,the non-methane hydrocarbon in the initial gaseous fuel stream toproduce a resultant fuel stream comprising the methane hydrocarbon andthe inert gas; mixing air at a second air mass flow rate into theresultant fuel stream downstream of the first catalyst and upstream of asecond catalyst; oxidizing, by the second catalyst, the methanehydrocarbon in the resultant fuel stream to produce an output fuelstream; and determining a value indicative of the methane hydrocarbon inthe initial gaseous fuel stream, a value indicative of the non-methanehydrocarbon in the initial gaseous fuel stream, and a value indicativeof the inert gas in the initial gaseous fuel stream. The determinationis based on the fuel mass flow rate, the first air mass flow rate, andthe second air mass flow rate.

Yet another embodiment relates to a system. The system includes a pump,a first mass flow device, a second mass flow device, a first catalyst, asecond catalyst, and a controller. The pump is structured to direct agaseous fuel stream over a first catalyst at a fuel mass flow rate. Thegaseous fuel stream includes a methane hydrocarbon, non-methanehydrocarbon, and an inert gas. The first mass flow control device isstructured to provide air at a first air mass flow rate to mix into thegaseous fuel stream upstream of the first catalyst. The first catalystpositioned to oxidize the non-methane hydrocarbon in the gaseous fuelstream to produce a resultant fuel stream comprising the methanehydrocarbon and the inert gas. The second mass flow control devicestructured to provide air at a second air mass flow rate to mix into theresultant fuel stream downstream of the first catalyst and upstream of asecond catalyst. The second catalyst is positioned to oxidize themethane hydrocarbon in the resultant fuel stream to produce an outputfuel stream. The controller is structured to determine a composition ofthe gaseous fuel stream based on the fuel mass flow rate, the first airmass flow rate, and the second air mass flow rate. Determining thecomposition of the gaseous fuel stream includes determining a valueindicative of the methane hydrocarbon in the gaseous fuel stream;determining a value indicative of the non-methane hydrocarbon in thegaseous fuel stream; and determining a value indicative of the inert gasin the gaseous fuel stream.

Another embodiment relates to an apparatus. The apparatus includes afirst mass flow controller, a second mass flow controller, and a mastercontroller. The first flow controller is structured to provide air at afirst air mass flow rate to mix into a fuel stream upstream of a firstcatalyst. The fuel stream is directed over the first catalyst at a fuelmass flow rate. The fuel stream includes a methane hydrocarbon, anon-methane hydrocarbon, and an inert gas. The a second mass flowcontroller is structured to provide air at a second air mass flow rateto mix into the fuel stream downstream of the first catalyst andupstream of a second catalyst. The master controller is communicably andoperatively coupled to each of the first mass flow controller and thesecond mass flow controller. The master controller is structured todetermine a composition of the fuel stream including a value indicativeof the methane hydrocarbon in the fuel stream, a value indicative of thenon-methane hydrocarbon in the fuel stream, and a value indicative ofthe inert gas in the fuel stream. The determination is based on the fuelmass flow rate, the first air mass flow rate, and the second air massflow rate. In one embodiment, the apparatus further includes an enginecontroller. The engine controller is structured to control operation ofan engine based on the composition of the fuel stream. The engine isstructured to combust a second fuel stream associated with the firstfuel stream.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the following drawings and thedetailed description.

BRIEF DESCRIPTION OF THE DRAW

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several implementations in accordance withthe disclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 is a block diagram of a system for determining the composition ofgaseous fuel, according to one embodiment.

FIG. 2 is a diagram of a system for determining the composition ofgaseous fuel, according to one embodiment.

FIG. 3 is a flow diagram of a process for determining the composition ofgaseous fuel, according to one embodiment.

FIG. 4 is a diagram of a system for determining the composition ofgaseous fuel, according to one embodiment.

FIG. 5 is a flow diagram of a process for determining the composition ofgaseous fuel, according to one embodiment.

FIG. 6 is a flow diagram of a general process for determining thecomposition of gaseous fuel, according to one embodiment.

FIG. 7 is a block diagram of a controller for implementing thetechniques disclose herein, according to one embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe figures, can be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and made part of this disclosure.

Described herein are techniques for determining the composition ofgaseous fuel. According to the disclosure herein the relative amounts ofmethane, non-methane hydrocarbons, and inert gases in a raw fuel streamcan be determined. Although the term “raw fuel” and “raw well head gas”in this context often refers to fuels that are obtained from wells, thepresent disclosure is not limited to such supplied fuels. The techniquesdisclosed herein may be utilized to assess any gaseous fuel supply. Forthe purposes of this disclosure, references to “inert gases” will beassumed to be carbon dioxide (CO2), which is an adequate surrogate,although other surrogate gas mixtures may be used. Accordingly, theseraw well head fuels can be characterized by the chemical formula:(CH4_(x)) (CnHμ_(y)) (CO2_(z)). Here, x represents the number of molesof methane per mole of fuel, y represents the number of non-methanehydrocarbons per mole of fuel, and z represents the number of moles ofinert gases per mole of fuel (with carbon dioxide being chosen as arepresentative “inert” gas). The non-methane hydrocarbons may be assumedto be represented by a single species of hydrocarbons having n moles ofcarbon per mole of non-methane hydrocarbon, and μ can represent thenumber of moles of hydrogen per mole of non-methane hydrocarbon. Ingeneral, a majority of raw well head gases can be represented bychoosing n=3 and μ=8 (i.e., propane), although the present disclosure isnot limited to such a configuration.

The disclosure herein also provides systems and devices that can monitorthe relative amounts of methane, non-methane hydrocarbons, and carbondioxide of the fuel stream entering an engine. Only a very small amountof the fuel stream entering the engine must pass through the systems ordevices. In one embodiment, only approximately 0.25 lb./hr. of raw fuelmust be processed by the systems or devices to perform their functions.This low rate of fuel is “sacrificial” and will not be used by theengine. Other fuel amounts may also be used. Once the relativeproportions of methane, non-methane hydrocarbons, and carbon dioxide inthe raw fuel are known (e.g., x, y, and z), parameters that characterizeengine performance can be computed. Such parameters typically includethe methane number, the lower heating value, the volumetric heatingvalue, and Wobbe index, among others. For example, a target ratio offuel-to-air and spark timing for optimal performance and emissionscompliance can be determined for a given engine by knowing the methanenumber and lower heating value of the fuel.

In general, when a raw fuel stream is directed over a typical oxidationcatalyst, methane in the fuel will pass through without being oxidized.A specially designed catalyst is required to oxidize methane.Additionally, carbon dioxide in the original raw fuel stream will passthrough both types of catalysts without being affected. However, if anappropriate amount of air is mixed with the raw fuel stream upstream ofthe typical oxidation catalyst, all non-methane hydrocarbons from theoriginal raw fuel stream can be oxidized, but the methane and carbondioxide present in the original raw fuel stream will pass throughunchanged. Then, if more air is added to the gases downstream of thetypical catalyst and upstream of the special catalyst, and if the amountof the air is adjusted appropriately, the methane can be fully oxidizedby the special catalyst. The carbon dioxide in the original raw fuelstream may again pass through the special catalyst unchanged.

According to the disclosure herein, the mass flow of the original rawfuel stream entering a device as disclosed herein, the mass flow of theair entering upstream of the typical catalyst, and the mass flow of theair upstream of the special catalyst may be known or determined, and theexact proportions of the methane, non-methane hydrocarbons, and thecarbon dioxide in the original raw fuel stream can be preciselydetermined. Various flow controllers may be used, as will be described,to allow a “correct” amount of air to be admitted to the streamsentering both catalysts. Combustion with the chemically correct amountof air is known as “stoichiometric” combustion, which implies that thefuel and air mixture has neither too much nor too little air, but justenough to fully oxidize the fuel into water and carbon dioxide.Throughout the disclosure herein, a typical oxidation catalyst may bereferred to as a Non-methane Hydrocarbon Catalyst, or a NMHC Catalyst. Aspecial catalyst that can oxidize urethane may be referred to as aMethane Oxidation Catalyst.

Referring to FIG. 1, a block diagram of a general system 100 fordetermining the composition of gaseous fuel is shown, according to oneembodiment. System 100 operates over a gaseous fuel stream 102 as thesource fuel. In one embodiment, fuel stream 102 comprises a raw well gasthat may be supplied to one or more engines. One or more mass flowcontrollers 104 may be used to control the flow of the fuel and addedair through system 100. A flow rate may be held constant or adjusted. Inone embodiment, the flow rate of fuel stream 102 is at a rate necessaryto maintain a stoichiometric combustion of the non-methane hydrocarbonsand the methane of the initial fuel stream by catalysts 106. The ratemay further be such that a chemically correct stoichiometric fuel to airratio is maintained. Multiple catalysts 106 may be used to oxidize thenon-methane hydrocarbons of fuel stream 102, and also to oxidize themethane of fuel stream 102. In one embodiment, a first catalyst is usedto oxidize the non-methane hydrocarbons and a second catalyst is used tooxidize the methane of fuel stream 102. One or more sensors 108 (e.g.,oxygen sensors) may be used to determine the amount of oxygen in fuelstream 102 as it flows through system 100 and is oxidized by catalysts106. In one embodiment, sensors 108 include zirconia based oxygensensors. One or more processors 110 may be used to control the flowprocess of fuel stream 102 and air throughout the system 100. Forexample, processors 110 may monitor, record (in Memory), and analyzevalues provided by sensors 108, and determined flow rates based on suchvalues. The processors 110 may generate the signals necessary to controlmass flow controllers 104 or communicate with any other components ofsystem 100. Additionally, processors 110 may determine the compositionof fuel steam 102 and generate reporting data and transmit data (via atransmitter or other communication connection) to external systems.

Referring to FIG. 2, a diagram of a system 200 for determining thecomposition of gaseous fuel is shown, according to one embodiment.System 200 includes an initial raw fuel stream 202. In one embodiment,fuel stream 202 is a gaseous fuel supplied by a well (which mayultimately be used by an engine). For example, a small amount of fuelfrom source fuel stream 202 is admitted to system 200. Air may then beadmitted 204 to fuel stream 202, where is can be mixed prior to beingintroduced into the NMHC Oxidation Catalyst 206. For example, a massflow controller may be electronically controlled in order to adjust therate of air admitted. Multiple components (e.g., pressure regulators,filters, etc.) may also be used in such a process of controlling the airflow. In one embodiment, the amount of air admitted at this point is theamount required to support stoichiometric combustion of the non-methanehydrocarbons present in the original raw fuel stream 202. Downstream ofthe NMHC Oxidation Catalyst 206, air may be admitted 208 to the streamof gases flowing out of NMHC Oxidation Catalyst 206 and mixed. Forexample, another mass flow controller may be electronically controlledin order to adjust the rate of air admitted. In one embodiment, a singlemass flow controller may be used to admit air, with multiple routings ofthe admitted air. Such an embodiment may include the necessary conduit,valves, etc., required to admit air to be mixed and properly route theadmitted air. In one embodiment, the amount of air admitted at thispoint is the amount required to support stoichiometric combustion of themethane present in the original fuel stream 202 by Methane OxidationCatalyst 210. After flowing through both NMHC Oxidation Catalyst 206 andMethane Oxidation Catalyst 210, the gases flowing from Methane OxidationCatalyst 210 may be exhausted via vent 212.

As NMHC Oxidation Catalyst 206 sloes not oxidize methane, the amount ofair admitted upstream of it (i.e., at 204) can be controlled to be thestoichiometric quantity needed to fully oxidize only the non-methanehydrocarbons of the original raw fuel stream 202. Additionally, theamount of air entering the stream of gases downstream of NMHC OxidationCatalyst 206 (i.e., at 208) can be controlled to be the stoichiometricamount required to fully oxidize all methane from the original raw fuelstream 202 by Methane Oxidation Catalyst 210. In one embodiment, system200 can require a determination of the mass flow rates of fuel and ofair in order to provide stoichiometric combustion of the non-methanehydrocarbons by NMHC Oxidation Catalyst 206. Additionally, the mass flowrate of air to provide stoichiometric combustion of the methane inMethane Oxidation Catalyst 210 may also be determined. In general, theamount of fuel entering system 200 is low (e.g., on the order of 0.25lb./hr., etc.), although this amount may vary.

A determination of the moles of methane per mole of fuel (x), the molesof non-methane hydrocarbons per mole of fuel (y), and the moles ofcarbon dioxide per mole of fuel (z), can be determined via process 300described in FIG. 3. In some embodiments, it may be necessary toestimate the number of moles of carbon per mole of non-methanehydrocarbons (n), and number of moles of hydrogen per mole ofnon-methane hydrocarbons (μ). However, in some embodiments it is assumedthat n=3 and μ=8, which represents propane, without sacrificingsignificant accuracy. Other values for n and μ may also be used ifdesired. In some embodiments, increased accuracy can be obtained if therelative humidity fraction (rh) of the combustion air admitted to system200 is known or determined, in general, valid values for rh aretypically between 0 and 1.

Referring to FIG. 3, a flow diagram of a process 300 for determining thecomposition of gaseous fuel is shown, according to an embodiment. Inalternative embodiments, fewer, additional, and/or different steps maybe performed. Also, the use of a flow diagram is not meant to belimiting with respect to the order of steps performed. Various functionsmay be utilized to compute the following values discussed throughoutprocess 300. Such functions are provided below, however, the presentdisclosure is not limited to use of the provided functions and othercomputations may be performed in order to obtain the discussed values.Process 300 includes providing non-hydrocarbon surrogate values 302. Inone embodiment, the surrogate values are chosen to be representative ofpropane (e.g., n=3 and μ=8). The mass flow rates may then be obtained(304). For example, a mass flow meter, a critical flow orificeconfigured to restrict flow of a fluid therethrough, or another flowrate control device may be used to control and determine the mass flowrate. The moles of water vapor per mole of oxygen in air may then becomputed (306). Additionally, the air mole weight may also be computed(306). Guess/estimate values for x, y, and z (i.e., estimates for thenumber of moles of methane per mole of fuel, the number of non-methanehydrocarbons per mole of fuel, and the number of moles of inert gasesper mole of fuel) may be provided (308). In one embodiment, the initialguess values may be based on a prior knowledge of reasonable values forx, y, and z corresponding to a particular configuration. The mole weightof the gaseous fuel may then be computed (310). Based on the abovedetermined values, computed values of y (the number of non-methanehydrocarbons per mole of fuel) and x (the number of moles of methane permole of fuel) can be determined (312). The fuel molar flow rate may thenbe computed (314). A computed value of z (the number of moles of inertgases per mole of fuel) may then be determined (316). For example, z maybe computed by finding the root of the function, zFunc(z), providedbelow. The computed values of x, y, and z may then be compared to theestimate values of x, y, and z (318). If the estimate values aresufficiently close to the computed values, process 300 may terminate.However, if the estimate values are not sufficiently close to thecomputed values, process 300 may iterate and the computed values for x,y, and z may be used during the next iteration (320).

After x, y, and z are computed (e.g., via process 300), criticalparameters of the original fuel stream can be determined. For example,the methane number, lower heating value, volumetric heating value, andWobbe index may be determined. The values may be provided to an enginecontroller or other external system (e.g., an operator's computingsystem). By providing one or more of these parameters, an engine can beset for optimal ratios of fuel-to-air flow as well as spark timing inorder to best accommodate the characteristics of the raw fuel stream.

Functions that may be utilized in the computation of process 300 (andprocess 500 of FIG. 5) are provided below:

wtrFunc(rh) = (−8.279417 ⋅ 10⁻⁴) + (1.600004 ⋅ 10⁻¹) ⋅ rhM_(Air) = (M_(O 2) + AirN 2 ⋅ M_(N 2) + AirCO2 ⋅ M_(CO 2) + wrt ⋅ M_(H 2O))${Mn}_{F} = \frac{{x \cdot M_{{CH}\; 4}} + {y \cdot \left( {{n \cdot M_{C}} + {\mu \cdot M_{H}}} \right)} + {z \cdot M_{{CO}\; 2}}}{x + y + z}$$M_{F} = \left( {{{x \cdot M_{{CH}\; 4}} + {y \cdot \left( {{n \cdot M_{C}} + {\mu \cdot M_{H}}} \right)} + {{z \cdot M_{{CO}\; 2}}k}} = {{{{kFunc}\left( {x,y,z,T_{F}} \right)}{mdot}_{F}} = {{{C \cdot A \cdot P_{F} \cdot \sqrt{k \cdot \left( \frac{{Mn}_{F}}{T_{F} \cdot {UPGC}} \right) \cdot \left( \frac{2}{k + 1} \right)^{(\frac{k + 1}{k - 1})}}}y} = {{\frac{4 \cdot M_{F} \cdot {mdot}_{{Air}\; 1}}{{M_{Air} \cdot \mu \cdot {mdot}_{Fuel}} + {4 \cdot M_{Air} \cdot {mdot}_{Fuel} \cdot n}}x} = {{\frac{M_{F} \cdot {mdot}_{{Air}\; 2}}{2 \cdot M_{Air} \cdot {mdot}_{Fuel}}F\; 1} = {{\frac{{mdot}_{Fuel}}{M_{F}}z} = {{root}\left( {{{zFunc}(z)},z} \right)}}}}}}} \right.$

The zFunc(z) computation is described below:

${{zFunc}(z)}:=\left. {{jnk}\; 1}\leftarrow{F\;{1 \cdot \left\lbrack {M_{F} + {\left\lbrack {{y \cdot \left( {n + \frac{\mu}{4}} \right)} + {2 \cdot x}} \right\rbrack \cdot M_{Air}}} \right\rbrack}} \right.$${{zFunc}(z)}:=\left. {{jnk}\; 2}\leftarrow{{\left\lbrack {{F\;{1 \cdot \left\lbrack {{{y \cdot \left( {n + \frac{\mu}{4}} \right) \cdot {{Air}{CO}}}\; 2} + {y \cdot n} + z} \right\rbrack}} + {2 \cdot \left( {F\;{1 \cdot x}} \right) \cdot \left( {\frac{1}{2} + {{{Air}{CO}}\; 2}} \right)}} \right\rbrack \cdot M_{{CO}\; 2}} + {\left\lbrack {{F\;{1 \cdot \left\lbrack {\frac{y \cdot \mu}{2} + {y \cdot \left( {n + \frac{\mu}{4}} \right) \cdot {wtr}}} \right\rbrack}} + {2 \cdot \left( {F\;{1 \cdot x}} \right) \cdot \left( {1 + {wtr}} \right)}} \right\rbrack \cdot M_{H\; 2O}}} \right.$${{zFunc}(z)}:={\left. {{jnk}\; 3}\leftarrow{{\left\lbrack {{F\;{1 \cdot \left\lbrack {y \cdot \left( {n + \frac{\mu}{4}} \right) \cdot {{AirN}2}} \right\rbrack}} + {2 \cdot \left( {F\;{1 \cdot x}} \right) \cdot {{Air}{N2}}}} \right\rbrack \cdot M_{N\; 2}}{{zFunc}(z)}} \right.:={\left. {out}\leftarrow{{{jnk}\; 1} - {\left( {{{jnk}\; 2} + {{nk}\; 3}} \right){{zFunc}(z)}}} \right.:={out}}}$

Definitions of variables that are used in implementing the abovefunctions are provided in Table 1. These parameters may be used indetermining the composition of a gaseous fuel stream as described herein(e.g., in processes 300 and 500, etc.).

TABLE 1 Parameter Description n Carbon number of non-methanehydrocarbons in fuel stream μ Hydrogen number of non-methanehydrocarbons in fuel stream mdot_(F) Mass flow rate of fuel streammdot_(Air1) Mass air flow rate entering NMHC Oxidation Catalystmdot_(Air2) Mass air flow rate entering Methane Oxidation CatalystAirtN2 Moles of nitrogen per mole of oxygen in air AirCO2 Moles ofcarbon dioxide per mole of oxygen in air rh Relative humidity fractionM_(Air) Molal weight of air M_(O2) Molecular weight of oxygen M_(N2)Molecular weight of nitrogen M_(CO2) Molecular weight of carbon dioxideM_(H2O) Molecular weight of water vapor Mn_(F) Molecular weight of fuelM_(F) Molal weight of fuel x Moles of methane per mole of fuel y Molesof non-methane hydrocarbons per mole of fuel z Moles of inert gases(e.g., carbon dioxide) per mole of fuel k Ratio of specific heats offuel T_(F) Temperature of fuel P_(F) Pressure upstream of fuel criticalflow orifice kFunc(x, y, z, T_(F)) Function to compute ratio of specificheats of fuel zFunc(z) Function to compute z of fuel

Referring to FIG. 4, a diagram of a system 400 for determining thecomposition of gaseous fuel is shown, according to one embodiment. Inthis embodiment, the mass flow rate of the raw fuel stream 402 can bedetermined using critical flow orifice 410. Raw fuel stream 402 may beinitially filtered (via filter 404). Any filter may be utilized to cleanfuel stream 402 prior to being processed. After being filtered, pump 406and pressure regulator 408, which are positioned upstream of thecritical flow orifice 410 can be used to maintain a certain pressureratio across the critical flow orifice 410 to ensure the flow isrestricted to a particular flow rate.

The amount of air needed to oxidize the non-methane hydrocarbons in theoriginal fuel stream 402, with NMHC Oxidation Catalyst 414 maintained atthe correct stoichiometric fuel and air ratio, may be controlled by afirst mass flow controller 412. Mass flow controller 412 receivesappropriate control signals from a master controller 432. In order togenerate the appropriate control signals, master controller 432 canmonitor the level of oxygen present in the gases downstream of the NMHCOxidation Catalyst 414. To do so, a first oxygen sensor 424 may providefeedback related to the product of oxidation by NMHC Oxidation Catalyst414. In one embodiment, NMHC Oxidation Catalyst 414 is designed toenable methane from the original raw fuel stream 402 to pass throughwithout change, along with the carbon dioxide from original raw fuelstream 402. Based on the products, master controller 432 can correctlycontrol mass flow controller 412 and can adjust the amount of airintroduced (and in turn adjust the oxidation of non-methane hydrocarbonsby NMHC Oxidation Catalyst 414). In one embodiment, oxygen sensor 424includes a “switching” zirconia based oxygen sensor (e.g., similar tothat typically used in automotive applications). However, other types ofoxygen sensors may be utilized. In one embodiment, master controller 432manages mass flow controller 412 by “dithering” the rate of air flow,first slightly below or above, then slightly above or below, the rate ofair flow necessary to maintain stoichiometric combustion of thenon-methane, hydrocarbons within NMHC Oxidation Catalyst 414. The“dithering” amount can be indicated by oxygen sensor 424 as it changesstate (e.g., from 0 to 1, etc.) when oxygen appears in the stream at itslocation (i.e., when slightly too much air 420 is admitted) and thenwhen oxygen disappears (i.e., when slightly too little air 420 isadmitted). Accordingly, master controller 432 may control a mass flowcontroller in response to data provided by an oxygen sensor.

The amount of air necessary to oxidize the methane from the original rawfuel stream 402 with Methane Oxidation Catalyst 426 at the correctstoichiometric fuel and air ratio can be controlled with a second massflow controller 422. In one embodiment, mass flow controller 422receives appropriate control signals from master controller 432. Mastercontroller 432 may monitor signals from a second oxygen sensor 428 inorder to correctly control mass flow controller 422. In one embodiment,oxygen sensor 428 includes a “switching” zirconia based oxygen sensor(e.g., similar to as described for oxygen sensor 424). Master controller432 manages mass flow controller 422 by “dithering” the rate of airflow, first slightly below or above, then slightly above or below, therate of air flow necessary to maintain stoichiometric combustion of themethane within Methane Oxidation Catalyst 426. The “dithering” amountcan be indicated by oxygen sensor 428 as it changes state (e.g., from 0to 1, etc.) when oxygen appears in the stream at its location (i.e.,when slightly too much air 420 is admitted) and then when oxygendisappears (i.e., when slightly too little air 420 is admitted), andmaster controller 432 may interpret the data from oxygen sensor 428 inorder to determine an amount of adjustment to be made to mass flowcontroller 422. The fuel stream 402 passes through Methane OxidationCatalyst 426, and the remaining fuel stream 402 may be vented via a vent430. In general, the air 420 discussed herein may be supplied from anyair source, and may be filtered (e.g., via an air filter 418, etc.)prior to being admitted to fuel stream 402. A pressure regulator 416and/or manifold may also be used to maintain a proper pressure and flowrate of air 420 to mass flow controllers 412 and 422.

Typically, non-methane hydrocarbon catalysts can function properly whenthe temperature of the catalyst is maintained at a temperature(generally a constant temperature) within a range of 250° C. to 350° C.A first electrical controller 434 may be employed to maintain NMHCOxidation Catalyst 414 at a particular temperature (e.g., within the250° C. to 350° C. range) by way of resistive heater elements encasingor coupled to the catalyst. Other heating mechanisms may also be usedand controlled by electrical controller 434. Catalysts capable ofoxidizing methane need to be maintained at a higher temperature,typically within the range of 550° C. to 650° C. Accordingly, a secondelectrical controller 438 may be used to maintain Methane OxidationCatalyst 426 a particular temperature (e.g., within the 550° C. to 650°C. range) by way of resistance heater elements encasing or coupled tothe catalyst. A min power source 436 may be used to supply power to theelectrical controllers (and to any of the other controllers discussedherein. In one embodiment, electrical controller 434 and electricalcontroller 438 are part of an electrical controller unit that is capableof managing the temperatures of both NMHC Oxidation Catalyst 414 andMethane Oxidation Catalyst 426. Master controller 432 may also interfacewith and control the electrical controllers.

Referring to FIG. 5, a flow diagram of a process 500 for determining thecomposition of gaseous fuel is shown, according to an embodiment. Inalternative embodiments, fewer, additional, and/or different steps maybe performed. Also, the use of a flow diagram is not meant to belimiting with respect to the order of steps performed. Process 500 maybe used to determine x, y, and z of a raw fuel stream supplied to asystem as described with respect to FIG. 4. Various functions may beutilized to compute the following values discussed throughout process500. Such functions are provided above, however, the present disclosureis not limited to use of the provided functions and other computationsmay be performed to obtain the discussed values. Process 500 includesproviding non-hydrocarbon surrogate values 502. In one embodiment, thesurrogate values are chosen to be representative of propane (e.g., n=3and μ=8). The mass flow rates may then be obtained (504). For example, amass flow meter, a critical flow orifice (e.g., critical flow orifice410) configured to restrict flow of a fluid therethrough, or anotherflow rate detection device may be used to determine the mass flow rate.The moles of water vapor per mole of oxygen in air may then be computed(506). Additionally, the air mole weight may also be computed (506).Guess/estimate values for x, y, and estimates for the number of moles ofmethane per mole of fuel, the number of non-methane hydrocarbons permole of fuel, and the number of moles of inert gases per mole of fuel)may be provided (508). The mole weight of the gaseous fuel may then becomputed (510). The ratio of specific heats of fuel may also be computed(512). The mass flow rate of the fuel stream may also be computed (514).Based on the above determined values, computed values of y (the numberof non-methane hydrocarbons per mole of fuel) and x (the number of molesof methane per mole of fuel) can be determined (516). The fuel molarflow rate may then be computed (518). A value of z (the number of molesof inert gases per mole of fuel) may then be computed (520). Forexample, z may be computed by finding the root of the function,zFunc(z), provided above. The computed values of x, y, and z may then becompared to the estimate values of x, y, and z (522). If the estimatevalues are sufficiently close to the computed values, process 500 mayterminate. However, if the estimate values are not sufficiently close tothe computed values, process 500 may iterate and the computed values forx, y, and z may be used during the next iteration (524). Upon theconclusion of the iteration of steps 510-524, critical parameters of theoriginal fuel stream can be determined. For example, the methane number,lower heating value, volumetric heating value, and Wobbe index may bedetermined Other parameters may also be determined.

Referring to FIG. 6, a flow diagram of a general process 600 fordetermining the composition of gaseous fuel is shown, according to anembodiment. In alternative embodiments, fewer, additional, and/ordifferent steps may be performed. Also, the use of a flow diagram is notmeant to be limiting with respect to the order of steps performed. Aninitial gaseous fuel stream is provided at a fuel mass flow rate (602).The initial fuel stream comprises methane, non-methane hydrocarbons, andinert gases. In one embodiment, the fuel stream is supplied from a well.Air is mixed into the initial fuel stream upstream of a first catalyst,where the air is at a first air mass flow rate (604). The first catalystthen oxidizes only the non-methane hydrocarbons of the initial fuelstream to produce a resultant fuel stream comprising methane and inertgases (606). Air is mixed into the resultant fuel stream downstream ofthe first catalyst and upstream of a second catalyst, where the air isat a second air mass flow rate (608). The second catalyst oxidizes onlythe methane hydrocarbons of the resultant fuel stream to produce anoutput fuel stream (610). A mole ratio of the methane of the initialfuel stream, a mole ratio of the non-methane hydrocarbons of the initialfuel stream, and a mole ratio of the inert gases of the initial fuelstream may then be each determined (612). For example, measurements maybe taken (e.g., using oxygen sensors, flow rate sensors, etc.) as thefuel stream flows and is oxidized as discussed above. Based on suchmeasurements, the mole ratios related to the composition of the gaseousfuel can be determined.

In any of the embodiments discussed herein, the controllers may form aportion of a processing subsystem including one or more computingdevices having memory, processing, and communication hardware. Thecontrollers may be a single device or a distributed device, and thefunctions of the controllers may be performed by hardware and/or ascomputer instructions on a non-transient computer readable storagemedium, and functions may be distributed across various hardware orcomputer based components. Referring to FIG. 7, a controller 700 isshown, which may be any of the controllers discussed herein. Controller700 may also be used to implement the techniques and methods discussedherein. For example, controller 700 may be master controller 432 of FIG.4. In addition, controller 700 may be configured to perform thecomputations discussed herein (e.g., the computations of processes 300and 500, etc.) and generate the signals necessary to interface withother devices in order to determine composition of gaseous fuel. Incertain embodiments, controller 700 is part of a sensor deviceconfigured to determine the composition of gaseous fuel. Such a devicemay include components as discussed herein (e.g., the components ofsystems 100, 200, or 400, etc.). In certain embodiments, controller 700is part of a single controller device that includes mass flowcontrollers and/or oxygen sensors.

Certain operations of controller 700 (or master controller 432)described herein include operations to interpret and/or to determine oneor more parameters. Interpreting or determining, as utilized herein,includes receiving values by any method known in the art, including atleast receiving values from a datalink or network communication,receiving an electronic signal (e.g. a voltage, frequency, current, orPWM signal) indicative of the value, receiving a computer generatedparameter indicative of the value, reading the value from a memorylocation on a non-transient computer readable storage medium, receivingthe value as a run-time parameter by any means known in the art, and/orby receiving a value by which the interpreted parameter can becalculated, and/or by referencing a default value that is interpreted tobe the parameter value.

As shown FIG. 7, controller 700 includes a processing circuit having aprocessor 702 and a memory 704. Processor 702 may be implemented as ageneral-purpose processor, an application specific integrated circuit(ASIC), one or more field programmable gate arrays (FPGAs), a digitalsignal processor (DSP), a group of processing components, or othersuitable electronic processing components. One or more memory devices704 (e.g., NVRAM, RAM, ROM, Flash Memory, hard disk storage, etc.) maystore data and/or computer code for facilitating the various processesdescribed herein. Thus, one or more memory devices 704 may becommunicably connected to processor 702 and provide computer code orinstructions to processor 702 for executing the processes described inregard to controller 700 herein. Moreover, one or more memory devices704 may be or include tangible, non-transient volatile memory ornon-volatile memory. Accordingly, the one or more memory devices 704 mayinclude database components, object code components, script components,or any other type of information structure for supporting the variousactivities and information structures described herein.

In addition, memory 704 may include memory storage physically locatedelsewhere, e.g., any cache memory in the processor 702 as well as anystorage capacity used as a virtual memory, e.g., as stored on a massstorage device, etc. Controller 700 may also include any additionalnetworking components or transmitters necessary to communicate withexternal configuration/control systems (e.g., Wi-Fi networkingcomponents, radiofrequency components, COM ports, sensorrelays/connections, etc.). For example, determined composition of agaseous fuel may be transmitted to an engine control unit or othercomputing system.

Memory 704 may further include various modules for completing theactivities described herein. More particularly, memory 704 may includevarious modules to determine a composition of a gaseous fuel. Whilevarious modules with particular functionality may be included in memory704, it should be understood that controller 700 and memory 704 mayinclude any number of modules for completing the functions describedherein. For example, the activities of multiple modules may be combinedas a single module, additional modules with additional functionality maybe included, etc. Further, it should be understood that controller 700may further control other activity beyond the scope of the presentdisclosure

Example and non-limiting module implementation elements include sensorsproviding any value determined herein, sensors providing any value thatis a precursor to a value determined herein, datalink and/or networkhardware including communication chips, oscillating crystals,communication links, cables, twisted pair wiring, coaxial wiring,shielded wiring, transmitters, receivers, and/or transceivers, logiccircuits, hard-wired logic circuits, reconfigurable logic circuits in aparticular non-transient state configured according to the modulespecification, any actuator including at least an electrical, hydraulic,or pneumatic actuator, a solenoid, an op-amp, analog control elements(springs, filters, integrators, adders, dividers, gain elements), and/ordigital control elements.

Communication between and among controller 700 and the components ofsystem 100, system 200, and/or system 400 may be via any number of wiredor wireless connections. For example, a wired connection may include aserial cable, a fiber optic cable, a CAT5 cable, or any other form ofwired connection. In comparison, a wireless connection may include theInternet, Wi-Fi, cellular, radio, etc. In one embodiment, a controllerarea network (CAN) bus provides the exchange of signals, information,and/or data. The CAN bus includes any number of wired and wirelessconnections. Because controller 700 is communicably coupled to thesystems and components in systems 100, 200, and/or 400, controller 700may receive data from one or more of the components shown in FIGS. 1, 2,and/or 4. For example, the data may include oxygen data, fuel flow data,air flow data, and/or temperature data acquired via one or more of thesensors (e.g., temperature sensors, oxygen sensors, flow sensors, etc.).

In general, the routines executed to implement the embodiments may beimplemented as part of an operating system or a specific application,module, or sequence of instructions. In certain embodiments, controller700 includes one or more modules structured to functionally execute theoperations to necessary to determine the composition of a gaseous fuelstream. The description herein including modules emphasizes thestructural independence of the aspects of a controller and illustratesone grouping of operations and responsibilities of a controller. Morespecific descriptions of certain embodiments of a controller'soperations are described by the sections herein referencing FIGS. 1-6.Other groupings that execute similar overall operations are understoodwithin the scope of the present application. The modules typicallycomprise one or more instructions set at various times in various memoryand storage devices in a computer, and that, when read and executed byone or more processors in a computer, cause the computer to performoperations necessary to execute elements of disclosed embodiments.Moreover, various embodiments have been described in the context offully functioning computers and computer systems, those skilled in theart will appreciate that the various embodiments are capable of beingdistributed as a program product in a variety of forms, and that thisapplies equally regardless of the particular type of computer-readablemedia used to actually effect the distribution. Examples ofcomputer-readable media include but are not limited to recordable typemedia such as volatile and non-volatile memory devices, floppy and otherremovable disks, hard disk drives, optical disks, flash memory, amongothers.

Example and non-limiting module implementation elements include thesensors, systems, and/or connections required to allow the controllersto determine the composition of gaseous fuel as discussed herein. Anysuch implementation elements each may be communicably coupled to thecontrollers and provide any value determined herein. Example andnon-limiting module implementation elements may further include devicesfor providing any value that is a precursor to a value determinedherein, data links and/or network hardware including communicationchips, oscillating crystals, communication links, cables, twisted pairwiring, coaxial wiring, shielded wiring, transmitters, receivers, and/ortransceivers, logic circuits, hard-wired logic circuits, reconfigurablelogic circuits in a particular non-transient state configured accordingto the module specification, any valve actuator including at least anelectrical, hydraulic, or pneumatic actuator, a solenoid, an op-amp,analog control elements (springs, filters, integrators, adders,dividers, gain elements), and/or digital control elements.

The schematic flow chart diagrams and method schematic diagramsdescribed above are generally set forth as logical flow chart diagrams.As such, the depicted order and labeled steps are indicative ofrepresentative embodiments. Other steps, orderings and methods may beconceived that are equivalent in function, logic, or effect to one ormore steps, or portions thereof, of the methods illustrated in theschematic diagrams.

Additionally, the format and symbols employed are provided to explainthe logical steps of the schematic diagrams and are understood not tolimit the scope of the methods illustrated by the diagrams. Althoughvarious arrow types and line types may be employed in the schematicdiagrams, they are understood not to limit the scope of thecorresponding methods. Indeed, some arrows or other connectors may beused to indicate only the logical flow of a method. For instance, anarrow may indicate a waiting or monitoring period of unspecifiedduration between enumerated steps of a depicted method. Additionally,the order in which a particular method occurs may or may not strictlyadhere to the order of the corresponding steps shown. It will also benoted that each block of the block diagrams and/or flowchart diagrams,and combinations of blocks in the block diagrams and/or flowchartdiagrams, can be implemented by special purpose hardware-based systemsthat perform the specified functions or acts, or combinations of specialpurpose hardware and program code.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom VLSI circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like.

Modules may also be implemented in machine-readable medium for executionby various types of processors. An identified module of executable codemay, for instance, comprise one or more physical or logical blocks ofcomputer instructions, which may, for instance, be organized as anobject, procedure, or function. Nevertheless, the executables of anidentified module need not be physically located together, but maycomprise disparate instructions stored in different locations which,when joined logically together, comprise the module and achieve thestated purpose for the module.

Indeed, a module of computer readable program code may be a singleinstruction, or many instructions, and may even be distributed overseveral different code segments, among different programs, and acrossseveral memory devices. Similarly, operational data tray be identifiedand illustrated herein within modules, and may be embodied in anysuitable form and organized within any suitable type of data structure.The operational data may be collected as a single data set, or may bedistributed over different locations including over different storagedevices, and may exist, at least partially, merely as electronic signalson a system or network. Where a module or portions of a module areimplemented in machine-readable medium (or computer-readable medium),the computer readable program code may be stored and/or propagated on inone or more computer readable medium(s).

The computer readable medium may be a tangible computer readable storagemedium storing the computer readable program code. The computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, holographic,micromechanical, or semiconductor system, apparatus, or device, or anysuitable combination of the foregoing.

More specific examples of the computer readable medium may include butare not limited to a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), a digital versatile disc (DVD), an opticalstorage device, a magnetic storage device, a holographic storage medium,a micromechanical storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, and/or storecomputer readable program code for use by and/or in connection with aninstruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signalmedium. A computer readable signal medium may include a propagated datasignal with computer readable program code embodied therein, forexample, in baseband or as part of a carrier wave. Such a propagatedsignal may take any of a variety of forms, including, but not limitedto, electrical, electro-magnetic, magnetic, optical, or any suitablecombination thereof. A computer readable signal medium may be anycomputer readable medium that is not a computer readable storage mediumand that can communicate, propagate, or transport computer readableprogram code for use by or in connection with an instruction executionsystem, apparatus, or device. Computer readable program code embodied ona computer readable signal medium may be transmitted using anyappropriate medium, including but not limited to wireless, wireline,optical fiber cable, Radio Frequency (RF), or the like, or any suitablecombination of the foregoing.

In one embodiment, the computer readable medium may comprise acombination of one or more computer readable storage mediums and one ormore computer readable signal mediums. For example, computer readableprogram code may be both propagated as an electro-magnetic signalthrough a fiber optic cable for execution by a processor and stored onRAM storage device for execution by the processor.

Computer readable program code for carrying out operations for aspectsof the present invention may be written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Java, Smalltalk, C++ or the like and conventionalprocedural programming languages, such as the “C” programming languageor similar programming languages. The computer readable program code mayexecute entirely on the user's computer, partly on the user's computer,as a stand-alone computer-readable package, partly on the user'scomputer and partly on a remote computer or entirely on the remotecomputer or server.

The program code may also be stored in a computer readable medium thatcan direct a computer, other programmable data processing apparatus, orother devices to function in a particular manner, such that theinstructions stored in the computer readable medium produce an articleof manufacture including instructions which implement the function/actspecified in the schematic flowchart diagrams and/or schematic blockdiagrams block or blocks.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Accordingly, the present disclosure may be embodied in other specificforms without departing from its spirit or essential characteristics.The described embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the disclosure is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A system, comprising: a pump structured to direct a gaseous fuel stream over a first catalyst at a fuel mass flow rate, wherein the gaseous fuel stream comprises a methane hydrocarbon, non-methane hydrocarbon, and an inert gas; a first mass flow control device structured to provide air at a first air mass flow rate to mix into the gaseous fuel stream upstream of the first catalyst; the first catalyst positioned to oxidize the non-methane hydrocarbon in the gaseous fuel stream to produce a resultant fuel stream comprising the methane hydrocarbon and the inert gas; a second mass flow control device structured to provide air at a second air mass flow rate to mix into the resultant fuel stream downstream of the first catalyst and upstream of a second catalyst; the second catalyst positioned to oxidize the methane hydrocarbon in the resultant fuel stream to produce an output fuel stream; and a controller structured to determine a composition of the gaseous fuel stream based on the fuel mass flow rate, the first air mass flow rate, and the second air mass flow rate, wherein determining the composition of the gaseous fuel stream includes: determining a value indicative of the methane hydrocarbon in the gaseous fuel stream; determining a value indicative of the non-methane hydrocarbon in the gaseous fuel stream; and determining a value indicative of the inert gas in the gaseous fuel stream.
 2. The system of claim 1, further comprising a first oxygen sensor positioned to acquire first oxygen data indicative of a presence or an absence of oxygen in the resultant fuel stream, wherein the controller is further structured to control the first mass flow control device to adjust the first air mass flow rate based on the first oxygen data.
 3. The system of claim 2, further comprising a second oxygen sensor positioned to acquire second oxygen data indicative of a presence or an absence of oxygen in the output fuel stream, wherein the controller is further structured to control the second mass flow control device to adjust the second air mass flow rate based on the second oxygen data.
 4. The system of claim 3, wherein the first oxygen sensor comprises a zirconia based oxygen sensor, and wherein the second oxygen sensor comprises a zirconia based oxygen sensor.
 5. The system of claim 1, wherein the first catalyst is maintained at a temperature within a range of 250 to 350 degrees centigrade.
 6. The system of claim 5, wherein the second catalyst is maintained at a temperature within a range of 550 to 650 degrees centigrade.
 7. The system of claim 1, wherein the gaseous fuel stream is a first gaseous fuel stream that is a portion of a second gaseous fuel stream, the system further comprising an engine structured to combust the second gaseous fuel stream.
 8. The system of claim 7, wherein the controller is further structured to control at least one of a fuel-to-air ratio and an ignition timing of the engine based on the composition of the first gaseous fuel stream.
 9. An apparatus, comprising: a first mass flow controller structured to provide air at a first air mass flow rate to mix into a fuel stream upstream of a first catalyst, wherein the fuel stream is directed over the first catalyst at a fuel mass flow rate, and wherein the fuel stream includes a methane hydrocarbon, a non-methane hydrocarbon, and an inert gas; a second mass flow controller structured to provide air at a second air mass flow rate to mix into the fuel stream downstream of the first catalyst and upstream of a second catalyst; and a master controller communicably and operatively coupled to each of the first mass flow controller and the second mass flow controller, wherein the master controller is structured to determine a composition of the fuel stream including a value indicative of the methane hydrocarbon in the fuel stream, a value indicative of the non-methane hydrocarbon in the fuel stream, and a value indicative of the inert gas in the fuel stream, wherein the determination is based on the fuel mass flow rate, the first air mass flow rate, and the second air mass flow rate.
 10. The apparatus of claim 9, further comprising an engine controller structured to control operation of an engine based on the composition of the fuel stream, wherein the fuel stream is a first fuel stream, and wherein the engine is structured to combust a second fuel stream associated with the first fuel stream.
 11. The apparatus of claim 9, wherein the first catalyst is positioned to oxidize the non-methane hydrocarbon in the fuel stream to produce a resultant fuel stream comprising the methane hydrocarbon and the inert gas, and wherein the second catalyst is positioned to oxidize the methane hydrocarbon in the resultant fuel stream to produce an output fuel stream.
 12. The apparatus of claim 9, wherein the first mass flow controller is further structured to adjust the first air mass flow rate based on first oxygen data indicative of an amount of oxygen downstream of the first catalyst and upstream of the second catalyst, and wherein the second mass flow controller is further structured to adjust the second air mass flow rate based on second oxygen data indicative of an amount of oxygen downstream of the second catalyst. 